A. Field of the Invention
The invention relates to a damper mechanism, particularly a damper mechanism for damping torsional vibrations in a power transmission system.
B. Description of the Background Art
A clutch disk assembly used in, for instance an automotive vehicle, is typically installed in a clutch mechanism such that the clutch disk assembly may be used in clutch engagement and clutch disengagement operations for transmitting torque from a flywheel to a transmission input shaft. The clutch disk assembly preferably also includes a vibration dampening function for absorbing and damping vibration transmitted from the flywheel. Generally, vibrations of a vehicle include idling noises (rattle), driving noises (acceleration/deceleration rattle and muffled noises) and tip-in/tip-out (low frequency vibrations). The clutch disk assembly has the above damper function for removing these noises and vibrations.
The idling noises are rattling noises which occur from a transmission when the transmission is in a neutral position, e.g., during waiting at traffic signals with clutch pedal off. This rattling occurs due to the fact that an engine torque is low in an engine idling range and engine combustion causes large torque variations in the idling range. In this state, gear contact occurs between an input gear and a counter gear of a transmission, and thereby noises are produced.
The tip-in/tip-out low frequency vibrations are large longitudinal vibrations of a vehicle which occur when a driver rapidly depresses or releases an accelerator with the clutch in an engaged, torque transmitting condition. If rigidity of a drive transmission system is low, torque transmitted to wheels is transmitted or reflected from the wheels back through the drive train creating large oscillations of torque.
In a state where no torque is transmitted (zero torque transmission), for instance during idling, the dampening characteristics of most clutch disk assemblies is such that idling vibrations cannot be adequately dampened creating corresponding noises, therefore, a low torsional rigidity is preferable in this region of zero torque transmission. Contrarily, it is necessary to maximize the rigidity of the torsion characteristics of the clutch disk assembly for suppressing the longitudinal vibrations of the tip-in/tip-out.
For overcoming the above problems, a clutch disk assembly which uses two kinds of springs for achieving vibration dampening characteristics in two separate stages has been developed. The structure of this clutch disk assembly includes three rotary members adapted to undergo relative rotary displacement with respect to one another. A first spring having a low rigidity elastically couples first and second rotary members. A second spring having more rigid or stiff characteristic elastically couples a third rotary member and the second rotary member. The clutch disk assembly is configured to have a low torsional rigidity and a low hysteresis torque in the first stage where the first spring is compressed. Vibrations exhibiting small angular displacement having a low torsion angle are dampened and therefore the clutch disk assembly can achieve an effect of preventing noises during idling. Since the torsional rigidity and the hysteresis torque are high in the second stage of a high torsion angle due to the stiffness of the second spring, the longitudinal vibrations at the time of tip-in/tip-out can be effectively damped.
Such a damper mechanism is already known where operation of a high hysteresis torque generating mechanism (friction generating mechanism) in the second stage is at least partially prevented when minute vibrations occur thereby allowing dampening of minute vibrations by a low hysteresis torque.
The angular displacement within the second stage of operation in which a large friction mechanism does not operate is very small and, e.g., about 2 degrees. This region of the second stage can be provided in the positive second stage, in which the input rotary member rotates or twists in the torque transmission direction (positive rotational direction) relatively to the output rotary member, and the negative second stage, in which the relative rotation occurs in the opposite direction (negative rotational direction). In the prior art, the same structure is used for limiting the operation of the large friction mechanism in both the positive and negative portions of second stages. Therefore, the torsion characteristics in positive and negative rotation directions, in which a high hysteresis torque does not occur in response to minute vibrations, have equal circumferential angles with respect to one another.
However, the angular displacement in the positive rotation direction within the second stage of operation which exhibits low hysteresis torque must be sufficiently large to prevent generation of high hysteresis torque in response to engine torque vibrations during normal driving. However, if in the positive rotation direction the low hysteresis torque is large, the negative direction characteristics of low hysteresis torque may be excessively large. Specifically, if the angular displacement in the negative rotation direction for generation of low hysteresis torque is large, it is may be impossible to generate high hysteresis torque on the opposite sides of the resonance frequency during deceleration, resulting in a large vibration peak.
An object of the invention is to provide a damper mechanism which overcomes the problems associated with a damper mechanism in which there is no difference between regions in positive and negative second stages where low a hysteresis torque is generated in response to minute torsional vibrations.
In accordance with one aspect of the present invention, a damper mechanism includes a first rotary member and a second rotary member coupled to the first rotary member for limited relative rotary displacement therebetween such that torque is transmittable therebetween. A damper mechanism is disposed between the first and second rotary members coupling the first and second rotary members together in a rotating direction. The damper mechanism is adapted to exhibit torsion characteristics in first and second stages of relative rotary displacement between the first and second rotary members. Displacement in the second stage causes the damper mechanism to exhibit a higher rigidity than displacement in the first stage. The damper mechanism is adapted to provide dampening in the first and second stages in response to displacement in both positive and negative rotation directions, positive rotation corresponding to rotation of the second rotary member in a rotational driving direction with respect to the first rotary member,, and the negative rotation corresponding to rotation of the second rotary member in a rotational direction opposite the rotational driving direction with respect to the first rotary member. A friction mechanism is adapted to generate friction in response to relative rotary displacement between the first and second rotary members in the second stage. A friction suppressing mechanism is adapted to operate in response to torsional vibrations that do not exceed a predetermined level in the second stage. The friction suppressing mechanism is adapted to stop operation of the friction mechanism in response to torsional vibration within a first angular range in the direction of positive rotation within the second stage, and the friction suppressing mechanism is further adapted to stop operation of the friction mechanism in response to torsional vibration within a second angular range in the direction of negative rotation within the second stage. The first angular range and the second angular range are different in magnitude.
In accordance with another aspect of the present invention, a damper mechanism includes a first rotary member and a second rotary member coupled to the first rotary member for limited relative rotary displacement therebetween such that torque is transmittable therebetween. A damper mechanism is disposed between the first and second rotary members coupling the first and second rotary members together in a rotating direction and adapted to exhibit torsion characteristics in first and second stages of relative rotary displacement between the first and second rotary members. Displacement in the second stage causes the damper mechanism to exhibit a higher rigidity than displacement in the first stage. The damper mechanism is adapted to provide dampening in the first and second stages in response to displacement in both positive and negative rotation directions. Positive rotation corresponds to rotation of the second rotary member in a rotational driving direction with respect to the first rotary member, and the negative rotation corresponds to rotation of the second rotary member in a rotational direction opposite the rotational driving direction with respect to the first rotary member. A friction mechanism is adapted to generate friction in response to relative rotary displacement between the first and second rotary members in the second stage. A first friction suppressing mechanism is adapted to operate in response to torsional vibrations that do not exceed a predetermined level in a first angular range within the second stage in the direction of positive rotation. The first friction suppressing mechanism is adapted to stop operation of the friction mechanism in response to torsional vibration within the first angular range in the direction of positive rotation within the second stage. A second friction suppressing mechanism is adapted to operate in response to torsional vibrations that do not exceed a predetermined level in a second angular range within the second stage in the direction of negative rotation. The second friction suppressing mechanism is adapted to stop operation of the friction mechanism in response to torsional vibration within the second angular range in the direction of negative rotation within the second stage.
Preferably, the second angular range has a different angular magnitude than the first angular range.
Preferably, the second angular range is smaller than the first angular range.
Preferably, the angular magnitude of the second angular range is approximately half of that of the first angular range.
In accordance with another aspect of the present invention, a damper mechanism includes a first rotary member (3) and a second rotary member (2) coupled to the first rotary member for limited relative rotary displacement therebetween, the second rotary member adapted to transmit torque to the first rotary member. A first intermediate plate (6) is disposed operably between the first and second rotary members. A first elastic member (7) elastically couples the first rotary member to the first intermediate member in a rotating direction. The first elastic member is compressible therebetween and defines a first stage of relative rotary displacement between the first and second rotary members. A second elastic member (8) elastically couples the first intermediate member to the second rotary member in the rotating direction. The second elastic member is more rigid than the first elastic member and the second elastic member is compressible therebetween defining a second stage of relative rotary displacement between the first and second rotary members. A second intermediate member (11) is frictionally engaged with the second rotary member such that the second intermediate member is slidable in the rotating direction relative to the second rotary member. A portion of the second intermediate member being adapted for contact with the second elastic member but is spaced apart from the second elastic member with the damper mechanism in a torsion free state. In positive and negative directions of rotary displacement occur within the second stage of relative rotary displacement between the first and second rotary members, the positive direction being a direction the second rotary member is displaced with respect to the first rotary member in a rotational driving direction, and the negative direction being a direction the second rotary member is displaced with respect to the first rotary member in a direction opposite the rotational driving direction. A first circumferential space (ACp) is defined between the portion of the second intermediate member and a first portion of the second elastic member with the damper mechanism in a torsion free state thereby preventing the second intermediate member from sliding on the second rotary member in response to compression of the second elastic member in the positive direction. A second circumferential space (ACn) is defined between the portion of the second intermediate member and a second portion of the second elastic member with the damper mechanism in a torsion free state thereby preventing the second intermediate member from sliding on the second rotary member in response to compression of the second elastic member in the negative direction. The first and second circumferential spaces are formed independently from each other.
Preferably, the second intermediate member is disposed between the first rotary member and the first intermediate member, and the first and second circumferential spaces are formed between the first and second intermediate members.
In accordance with still another aspect of the present invention, a damper mechanism includes an output hub (3) and a pair of input plates (21, 22) rotatably disposed about the output hub. A first intermediate member (6) is rotatably disposed radially outward from the output hub, the first intermediate member further being disposed axially between the pair of input plates. A first elastic member (7) elastically couples the output hub to the first intermediate member limiting relative rotary displacement therebetween. Compression and expansion of the first elastic member define a first stage of relative rotary displacement between the input and output plates. A second elastic member (8) elastically couples the first intermediate member to the pair of input plates limiting relative rotary displacement therebetween. The second elastic member is more rigid than the first elastic member. Compression and expansion of the second elastic member defines a second stage of relative rotary displacement between the input and output plates. A second intermediate member (11) is disposed axially between the output hub and the pair of input plates. The second intermediate member is adapted for frictional engagement with at least one of the pair of input plates such that the second intermediate member generates friction in response to relative rotary displacement with the one of the pair of input plates. Relative rotary displacement between the input plates and the output hub occurs in both positive and negative directions. In the positive direction the input plates rotate relative to the output hub in a rotational driving direction, and in the negative direction the input plates rotate relative to the output hub in a direction opposite the rotational driving direction. A first circumferential space (ACp) is defined between the portion of the second intermediate member and a first portion of the second elastic member with the damper mechanism in a torsion free state thereby preventing the second intermediate member from sliding on the one of the input plates in response to compression of the second elastic member in the positive direction. A second circumferential space (ACn) is defined between the portion of the second intermediate member and a second portion of the second elastic member with the damper mechanism in a torsion free state thereby preventing the second intermediate member from sliding on the one of the input plates in response to compression of the second elastic member in the negative direction. The first and second circumferential spaces are formed independently from each other.
Preferably, the second intermediate member includes a pair of plate members (11) arranged on axially opposite sides of the first intermediate member, and a coupling member (62) connects the pair of plate members such that the pair of plate members rotate together. The first intermediate member is formed with at least one aperture (69), the coupling member extending through the aperture. The first and second circumferential spaces are defined between the aperture and the coupling member.
Preferably, a first stop mechanism (9) is defined between the pair of input plates and the output hub, the first stop mechanism defining a range of relative rotary displacement between the pair of input plates and the output hub within a first space angle. A second stop mechanism (12) is defined between portions of the pair of input plates and the second intermediate member, the second stop mechanism allowing relative rotary displacement between the pair of input plates and the second intermediate member only within a second space angle. A third stop mechanism (14) is defined between portions of the second intermediate member and the first intermediate member, the third stop mechanism allowing relative rotary displacement only within a third space angle formed between the second intermediate member and the first intermediate member. The first and second circumferential spaces are each an angular range of displacement that is equal to the third space angle minus the difference between the first space angle and the second space angle.
Preferably, the first and second circumferential spaces are defined by different circumferential angles.
Preferably, the second circumferential space is smaller than the first circumferential space.
Preferably, the second circumferential space is approximately half of the first circumferential space with respect to size.
According to the damper mechanism described above aspect, the first and second friction suppressing mechanisms are independent of each other. Therefore, the first angular range defined by the first friction suppressing mechanism can be different from the second angular range defined by the second friction suppressing mechanism without difficulty. Accordingly, each of the first and second angular ranges can be appropriately determined in the second stage. As a result, the peak of vibrations at the resonance frequency can be reduced during deceleration.